Pressure transducer

ABSTRACT

A pressure transducer is provided suitable for high-pressure fluids which includes a relatively straight tube to which pressure is supplied internally, the tube being of unsymmetrical cross section and reduced in size along one side thereof for deflection upon increase of pressure applied therein, a linear variable differential transformer preferably being provided for takeoff of displacement in response to pressure change.

niiei l Min Mnefleorge [451 Jan, 1 W72 [54] WRESMJE TMANSDUCE [72] Inventor: Willilnm l1). MncGeorge, Doylestown, Pa. [73] Assignees: Testing Technology Corporation,

Langhorne, Pa.

[22] Filed: Dec. 6, 11969 [21] Appl. No: 663,1741

[52] 11.8. C1. ..73/398 11 [51] ..G01l9/10 [58] Field ollSearch ..73/398 12,418,407; 92/92 [56] References Cited UNITED STATES PATENTS 2,222,259 11/1940 Hoffmann et a1 ..73/388 2,702,053 2/1955 Baker ..73/407 X Whittaker et a1 ..73/398 Cherniak ....73/398 X 3,412,387 11/1968 Miller ....73/41B X 3,481,254 12/1969 Wetherbee, Jr. ..92/92 745,636 9/1898 Luscomb ..73/418 Primary Examiner-Donald O. Woodie-l Attorney-Zachary T. Wobensmith, 2nd

[57] AWSTEEAQT A pressure transducer is provided suitable for high-pressure fluids which includes a relatively straight tube to which pressure is supplied internally, the tube being of unsymmetrical cross section and reduced in size along one side thereof for deflection upon increase of pressure applied therein, a linear variable differential transformer preferably being provided for takeoff of displacement in response to pressure change.

6 Claims, 5 Drawing ll igum BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to pressure transducers.

2. Description of the Prior Art It has heretofore been proposed to use tubes of elliptical cross section curved between their ends with pressure supplied thereto at one end and with a linkage at the free end for movement responsive to change of pressure within the tube, these being commonly known as Bourdon tubes.

It has also heretofore been proposed as in the patents to Laimins U.S. Pat. No. 3,046,788 and to Mulcahy et al., US. Pat. No. 3,286,526 to employ linear tubes but as therein shown the measurement is made transversely of the tube rather than by change of position of the free end thereof.

SUM Y OF THE INVENTION In accordance with the invention, a pressure transducer is provided having a linear tube of unsymmetrical cross section with pressure applied to the interior thereof, the free end of the tube moving with change of internally applied pressure, the deflection preferably being measured by a linear variable differential transformer.

It is the principal object of the present invention to provide a pressure transducer which is simple in construction, reliable in its action, which can be used for a wide range of pressures, and which has a high order of linearity and low hysteresis effeet in the operating range.

It is further object of the present invention to provide a pressure transducer which will have a high sensitivity with overrange.

Other objects and advantageous features of the invention will be apparent from the description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS The nature and characteristics features of the invention will be more readily understood from the following description taken in connection with the accompanying drawings forming part thereof, in which:

FIG. I is a view in perspective of a pressure transducer in accordance with the invention with the protective cover removed;

FIG. 2 is a fragnentary vertical sectional view taken approximately on the line 2-2 of FIG. I;

FIG. 3 is a fragmentary vertical sectional view taken approximately on the line 3-3 of FIG. 2;

FIG. I is a horizontal sectional view, enlarged, taken approximately on the line II-41 of FIG. I; and

FIG. 5 is a horizontal sectional view taken approximately on the line 5-5 ofFIG. I.

It should, of course, be understood that the description and drawings herein are illustrative merely and that various modifications and changes'can be made in the structure disclosed without departing from the spirit of the invention.

Like numerals refer to like parts throughout the several views.

DESCII l" 1 ON OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawings, a base I is provided having a tubular post or support II secured to and extending therefrom and substantially parallel thereto a linear pressure-responsive tube 112 which is also secured in the base III.

The base III has a fluid passageway M therein extending to and communicating with the lower end of the tube I2 and has a threaded porfion I for connection of a pressure line (not shown) to apply the pressure to be measured.

The tube I2 is closed at its free end by a plug 16.

The tube I2 as shown more particularly in FIG. 4 is unsymmetrical in cross section so that one side thereof is weaker or less stiff and therefore has a greater tendency to bend or bow on the weaker side. While the shape of the tube I2 can be varied it is preferred that for approximately half its circumference it is reduced in diameter as at I7 to about one-half the diameter of the other half of its circumference.

The motion of the end of the tube I2 at which the plug I6 is mounted can be measured in any desired manner but it is preferred to secure an arm Ih thereto, such as by a screw I9.

The ann Ih has a bracket 20 carried thereby with spaced downwardly extending tabs 2I and 22.

The tabs 21 and 22 have aligned openings 23 through which mounting ends 22 and 25 of a core 26 extend. The end M can be in threaded engagement in the tab 2I and a head 27 on the end 25 can be utilized for varying the position of the core 26 in the bracket 20.

The support II has a coil clamp 30 carried thereon. The clamp 30 has a central opening 31 for the reception of the coil 32 of a linear variable differential transformer. A slot 33 ex tends from the opening 31 and a bolt 3% is provided extending in intersecting relation to the slot 33 and in threaded engagement at 35. The head 36 of the bolt 34l engages he outside of the clamp 30. Tightening of the bolt 34l permits of removably clamping the coil 32 in place. The coil 32 has a central opening 3'7 through which the core 25 extends for movement therein.

The base I0 is preferably provided with a shoulder III for the reception of a cylindrical cover (not shown).

The mode of operation will now be pointed out.

Pressure fluid from the source whose pressure is to be measured is applied to the passageway It and therefrom into the interior of the pressure tube I2.

The tube 12, upon the application of pressure therein, has the free end thereof moved as determined by the magnitude of the pressure applied therein and for a specific cross section of the tube I2. In a specific embodiment the pressure may range from 500 to 20,000 psi. with a linearity of 10.1 percent full scale, and with hysteresis less than 0.1 percent full scale.

The movement of the free end of the: tube 12 is transferred by the bracket 20 to core 25 which by its movement in the coil 32 provides a variable output signals from the coil 32 which gives a measure of the pressure effective within the tube I2 and deflecting the free end thereof.

It will thus be seen that apparatus has been provided for effecting the objects of the invention.

Iclaim:

I. A pressure transducer comprising a base,

an elongated unitary substantially straight pressure-responsive tube fixedly mounted at one end in said base and having a closed free end,

a fluid connection in communication with said fixedly mounted end,

said tube along opposite sides thereof having elongated portions of different wall thicknesses to provide a different stiffness along one side thereof for substantially linearly moving the free end of said tube with increase of curvature upon increase of pressure,

said portions having different radii to determine the respective wall thickness of said tube, he portion of geater radius corresponding not more than half the circumference of the tube, and

motion-responsive means actuated by the free end of said tube.

2. A pressure transducer as defined in claim I in which said last-mentioned means includes a linear variable differential transformer.

3. A pressure transducer as defined in claim 2 in which said transformer has a fixed coil portion supported on said base and a movable core positioned by the free end of said tube.

I. A pressure transducer as defined in claim I in which said base has a post carried thereby, and

said post carries a fixed coil, and

said tube carries a core disposed within said coil and movable by the free end of the tube.

5. A pressure transducer as defined in claim 1 in which said motion-responsive means provides a signal responsive to change of position of said free end.

6. A pressure transducer as defined in claim 1 in which said tube is of circular exterior cross section. 5

i i i i k UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa e o, 3,635,090 Dated January 18, 1972 Inventor D Q It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

SPECIFICATION Column 2,

Line 20, after "engages" "he" should be the Claim 1,

Line 59, before "portion" "he" should be the Line 60, after "corresponding" 'toshould be inserted.

Signed and sealed this 30th day of May 1972.

Attest:

EDWARD MELETGHER, JR. ROBERT TT HALK Attesting Officer Commissioner of Patents USCOMM'DC 60376-PG9 U.S. GOVERNMENT PRINTING OFFICE: Hi9 0-356-33l F ORM PO-IOSO (10-69) 

1. A pressure transducer comprising a base, an elongated unitary substantially straight pressure-responsive tube fixedly mounted at one end in said base and having a closed free end, a fluid connection in communication with said fixedly mounted end, said tube along opposite sides thereof having elongated portions of different wall thicknesses to provide a different stiffness along one side thereof for substantially linearly moving the free end of said tube with increase of curvature upon increase of pressure, said portions having different radii to determine the respective wall thickness of said tube, he portion of greater radius corresponding not more than half the circumference of the tube, and motion-responsive means actuated by the free end of said tube.
 2. A pressure transducer as defined in claim 1 in which said last-mentioned means includes a linear variable differential transformer.
 3. A pressure tRansducer as defined in claim 2 in which said transformer has a fixed coil portion supported on said base and a movable core positioned by the free end of said tube.
 4. A pressure transducer as defined in claim 1 in which said base has a post carried thereby, and said post carries a fixed coil, and said tube carries a core disposed within said coil and movable by the free end of the tube.
 5. A pressure transducer as defined in claim 1 in which said motion-responsive means provides a signal responsive to change of position of said free end.
 6. A pressure transducer as defined in claim 1 in which said tube is of circular exterior cross section. 